The compounds of the present invention are inhibitors of Angiotensin-Converting Enzyme (ACE). ACE is a peptidyl dipeptidase which catalyzes the conversion of angiotensin I to angiotensin II. Angiotensin II is a powerful vasopressor which also stimulates aldosterone secretion by the adrenal cortex.
Inhibition of ACE lowers levels of angiotensin II and thus inhibits the vasopressor, hypertensive and hyperaldosteronemic effects caused thereby. It is known that inhibition of ACE is useful in the treatment of patients suffering from disease states such as hypertension and chronic congestive heart failure [See William W. Douglas, "Polypeptides - Angiotensin, Plasma Kinins, and Others", Chapter 27, in GOODMAN AND GILLMAN'S THE PHARMACOLOGICAL BASIS OF THERAPEUTICS, 7th edition, 1985, pp. 652-3, MacMillan Publishing Co., New York, N.Y.]. In addition, it has been disclosed that ACE inhibitors are useful in treating cognitive disorders [German Application No. 3901-291-A, published Aug. 3, 1989].
Certain tricyclic compounds such as that described by Flynn et al. [J. Amer. Chem. Soc. 109. 7914-15 (1987)] and Flynn and Beight [European Patent Application Publication No. 0 249 223 A2, published Dec. 16, 1987] are known as ACE inhibitors. The compounds of the present invention differ from these tricyclic inhibitors of ACE by having an amino or nitro substituent on the aromatic moiety of the tricyclic structure.
It has now been found that the amino or nitro substituted compounds of the present invention possess an unexpectedly prolonged duration of activity in comparison to other ACE inhibitors of similar structure.